[H-].[Na+].Br[CH2:4][CH2:5][CH2:6][CH2:7][CH2:8]Br.[Br:10][C:11]1[CH:16]=[C:15]([Br:17])[CH:14]=[C:13]([CH2:18][C:19]#[N:20])[C:12]=1[O:21][CH3:22].Cl>CN(C)C=O.O>[C:19]([C:18]1([C:13]2[CH:14]=[C:15]([Br:17])[CH:16]=[C:11]([Br:10])[C:12]=2[O:21][CH3:22])[CH2:8][CH2:7][CH2:6][CH2:5][CH2:4]1)#[N:20]
To a stirred suspension of sodium hydride (7 g) in dry dimethylformamide (200 ml) was added a solution of 1,5-dibromopentane (20 ml) and the product of stage (d) in dimethylformamide (40 ml), keeping the temperature at 20°-30° C. The mixture was stirred for 30 minutes, water was added cautiously, and was then poured into ice water. Hydrochloric acid was added and the mixture was extracted with dichloromethane, washed with water and brine, dried over magnesium sulphate and filtered, and the solvent was removed to give a pale brown oil which slowly crystallised. Recrystallisation from ethanol gave the title product as yellow crystalls, mp 100°-102° C.
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